Poly(ethylene glycol), also known as PEG, is useful in a variety of technological areas and is generally known by the formula HO—CH2CH2O—(CH2CH2O)n—CH2CH2—OH, wherein n typically ranges from about 3 to about 4000. In particular, there is great interest in utilizing PEG, and derivatives thereof, in the pharmaceutical and biomedical fields. This interest stems from the fact that PEG is nontoxic, biocompatible, non-immunogenic, soluble in water and other solvents, and is amenable to a variety of therapeutic applications including pharmaceutical formulations and drug delivery systems, among others.
One such area of interest relates to “PEGylation” which refers to the modification of other molecules, especially biomolecules, using PEG and derivatives thereof. PEGylation is often utilized in order to impart the desirable characteristics of PEG to a particular molecule. Such molecules have included proteins, dyes, peptides, hydrogels, and drugs, to name but a few. In the case of drugs, the formation of drug-polymer conjugates is also of interest. In addition, PEGylation has been utilized to attach PEG to other groups such as surfaces and cells.
The two terminal hydroxyl groups of PEG are readily available for chemical modification (e.g., for coupling to a protein or drug). However, this process requires the further functionalization of the PEG terminus in order to affect coupling to another molecule. Furthermore, because PEG contains two terminal hydroxyl groups it is often necessary to protect one of those hydroxyl groups in order to functionalize the other hydroxyl group. Thus, the current process of PEGylation typically requires multiple steps and results are often unpredictable.
Accordingly, it would be advantageous to provide heterobifunctionalized PEG's which are useful for PEGylation and are readily obtained directly from the polymerization reaction.